High temperature resistant coatings have been used to protect (e.g., thermal, oxidation and hot corrosion protection) high temperature components in gas turbines and diesel engines. Such coatings have been used to delay thermally-induced failure mechanisms that can impact the durability and life of such high temperature engine components. Plasma spraying (e.g., DC-arc) techniques have been used to deposit such thermal barrier coatings (i.e., TBCs). This process involves melting a feedstock material in a plasma plume and rapidly transporting the resulting molten particles so as to “splat” against a substrate surface. The molten particles typically solidify rapidly upon contacting the substrate surface. Successive build-up of these “splat” particles has resulted in a layered arrangement of the particles in the deposited coating, where the splats are entwined in complex arrays that generally have a brick-wall-like structure. These splats are separated by inter-lamellar pores resulting from rapid solidification of the lamellae, globular pores formed by incomplete inter-splat contact or around un-melted particles, and intra-splat cracks due to thermal stresses and tensile quenching stress relaxation. These pores and cracks interfere with the direct flow of heat (thermal barrier) resulting in lowered thermal conductivity. The cracks also increase the overall compliance of the coating and enhance the thermal shock resistance.
The present invention is an improvement in methods used to apply such coatings and in the resulting coatings themselves.